Trigger mechanism



A118- A7, 1945 R. v. SHEPHERD ETAL 2,381,521

TRIGGER MECHANISM Filed Sept. 9, 1942 @M @4MM www Patented Aug. 7, 1945 f "rRIGGiaR n o Regie-n fvernonlshephera and yHarold John l .v z 1 .pTurpin, London,-England y f Applieatiospteniber 9, 1942,/'sr'ial `N.,4"5'7,'792 In Great Britain April '17.1941 (Cl. i12-f) f solaires.

This invention relates to'machine'g'uns or rifles,

fand-lhas'as its'main object, to simplify the cons'tructio'n thereof, so as to-facilit'atemanufacture by'mass production methods. Whilst not limited @thereto-,Lrt'h'e invention is; particularly 'applicable t'ima'chihefcarbinsg i. e., short-barrelv machine 'gunsfw l f i" ,j' One object of the invention is to provide-fan l*improved 'trigger mechanism vwhichI is simple in action', has vrelativel'y'few moving parts;` and can.

:readily'and Lcheaply be produced by mass pro- ,-duction rmethods.' Such 'an improved trigger .mechanism-:may comprise an actuating lever for ftransmitting movement ofthe trigger tothe Sear, this/Jever. also lacting as I* a i member for vselecting zeitherrautomatic 'or single shot firing of the gun lWllenfthe triggerriSbperated.l 'Preferably the .actuatinglever constitutes the sole operating Vmember between'the triggerand the'sear. v

y :The vinventionfmay ibe 'carried into"v practice in @various ways, and 'one I convenient kvconstruction fon machine carbine' in accordance therewith will now be described b'y way' of example with referrence-to theiaccompanyingfdrawing in which- Fig. l is a' longitudinal sectional -vi'ewoff 'a construction embodying the invention, the' bolt'being 'Shown "imv an;- intermediate i position lbetween the vc ocyked-position a'nd the ringposition'; ali-ig l2fis aftransverse section taken on the line 2--2'ofy-i-Eig". 1.-, certain partsibeingfremoved; v'and fig.f3v isatransverse 'section taken on the line v3?-3 ,of .li"ig..` 1;.; with the mechanism' adjusted for lauto-matic `fring. .,--V.' Ihe 'construction'of carbine "shown in these igures-comprisesa tubular meta-l casing A exitendingv rearwardly from the breech end of the `barrel .which contains the bolt D which is of substantially rcylindrical form and ts within the casing.- so .thatit can reciprocate freely.y v'Ihe bolt `is relatively 'he'avy, and "thushas alarge inertia.

.cient time delay for the bullet to leave the barrelv before vthere is an appreciable thebolt andthenbarrel;

'rhe rear end of the bolt hasy a shank D8 of `recliucecl diameter forinsertion into the front end opening between of the helical return spring D1; In'the neighboi-irhood" ofthe;slfoi'ilclrerv thus formed, there is la vtransverse hole to receive the` shank of a cooking handlev D9 whichy projects through a slot in the casing f A.

kThe rearfen'd ofthe casing A is open and the rear abutment'oftheI spring D1 is constltuted by Aa removable cup A2 which fits within and closes vthe end'ofthe casing.l The cup A? is heldin position by a front'end'plate C1 onthe removable buttpart of which `is` shown at C and at the same time 'acts Aas 'a retaining catch for the butt. The cup A2 has a rearwardly projecting boss ornspigot A3 which engages in 'ahole'in the buttplate C1 so asto prevent further rotational movement ofthe plate when it has been positioned on the end o f the casing. The 'butt plate Cl'also has a pin C3 to engage in a slotI` H1 in the rear walll H of a trigger mechanism casingattached to thev underside 'of the casing A, the arrangement being such thatthe pin C3 enters the slot H1 when the plate C1;is inclined (in a plane perpendicular to the barrel axis) to its norma] position.v Rotation of the -butt to bring the hole in the butt plate Cl into alignment with the boss A3locks the' pin fand slot .connection and `at the same time brings the upper edge of lthe plate Cl under an overhung flange ,A4 fixed to or forming part of the main casing. The pin and slot connection C3-I-I1 in Aconjuncticm with the overhung viiange A4 thus prevent rear- .ward movement ofthe plate-C, and therefore of the abutment cup A2 of the return spring, whilst .the bossA3 on the cup prevents unlocking yrotacap may be formed separately, the skirt being in the form of a cylinder with its rear end extending into the cup, fullered and fastened to `the inside wall ofl the cup, for example byl spot welding or by riveting. I

Preferably, as shown in Figure 1, the rear surface of ,the cup A? abuts against a removable cap A7 which closes the end of the main'casingvand is held in position" by the front end plate `of the removable butt. 'The cap A'7 has a centralhole through which .the boss A3 projects to engagein the hole in the butt plateCl.. i The cap A'lretains the cup A2 and associated sleeve A6 in the end 0f the casing when the butt plate C1 is removed by pressing the spigot A3 and rotating the butt C' as described above.

The trigger mechanism casing is mounted on the underside and at the rearend of the main casing and consists of a pair of parallel vertical side walls H2H3, having their upper edges welded or otherwise fixedI to the main casing, and the v rear wall H'sc'ontai'ningas h'as'already been described, the slot H1 for the fixing pin on thebutt plate. The mechanism itself comprises a trlgger J pivoted at J1 between the side walls near the rear edge thereof, a sear K pivoted at K1 between the walls near the front edge thereof, J2 on the trigger J andextending forwardly therefrom so as to constitute the sole operating member between the trigger J and the sear K and also to act, in a manner to be described, as a member for` selecting single shot or automatic `firing of the carbine when the trigger is pressed.

In addition the mechanism includes a member .L1 for controllingthe selection by the actuating lover L. a tension spring L2 extending `between Ithe trigger .land the searK, and a bell crank lever .K2 pivoted on the sear for transmitting force exerted by the spring to the actuating lever.

'I'hetrigger J. comprises a stamping bent so as to havea crossfsection of substantially channel form in4 order to give it.rigidity, the sides of the channeltapering from a maximum width near theupper part of the trigger the pivot J1 at which comprises a horizontalpin supported in holes in the side wallsof the mechanism casing, to a minimum width at the lower operating part of the...- .trigger. At the upper end of the trigger the web is ,cut `away at J3 to provide afclearance space for the lever L the pivot J2 for which is fixed in the sides of the channel. A part 'J1 of the web below the pivot J1 is stamped out to form a hook for the tensionv spring L2 which extends forwardly and channel and are bent outwardly so as to engage the inner surfaces of the walls H2H3 and thus to -centre the trigger between the walls.

vThe trigger guard J8 consistsof a metal strip having a width equal to the distance between the inner surfaces of thej w'alls H2H3 and bent into substantially U-shape. The ends of the strip are inserted between the walls and are welded or votherwise fixed in position so that they also act as distance pieces'for maintaining the lower edges of the side walls the correct distance apart. rIhe trigger guard is positioned so that the rear limb trigger casing. The end of the trigger casing in front of the front limb of the guard lis closed by means of a hand grip of wood' M, or of a moulded material such as' the material sold under the registered trade-mark Bakelite, which covers -the forwardpart of the trigger casing and part of the lower surface of the main casing A, this grip being held in place by screw threaded studs. The hand grip M when inposition, also prevents withdrawalof the pivot pins J1 and K1vfor the trigger and an actuating lever Ly pivoted at.

'is close to the back plate H and the strip thus I protects and'in part closes the lower edge of the- J and the sear K, the pin J1, since its ends are not normally covered by the hand grip M, being arranged to project from one side wall of the casing and being bent over, as indicated by the broken line J9 in Figure 1, so as to extend substantially along the outside of the wall H3 to a point beneath the hand grip M. Preferably the end of the extension of the pin is turned inwardly so as to engagein a hole or recess J1in the side wall H3.

The sear K consists of a two-armed bell crank lever pivoted between the side walls so that the upper arm K3 extends rearwardly and substan tially horizontally, whilst the lower arm K1 extends downwardly. Rotation of the scar in a f countereclockwise direction thus tends to move a nose K5 on the upper surface of the horizontal arm through an aperture in the underside of the main casing A into the path of a lug D11 on the underside of the bolt. The lower end of the arm 'K'1 is of reduced width so as to form a step K6 about half wayvbetween the pivot K1 and the end of the arm. This step constitutes a projection or lug which normally engages in a notch L3 in the lever L so that the longitudinal forward movement of lever L as thetrigger J is depressed causes clockwise rotation of the Sear K about its pivot to lower the nose K5 and thus release the ,bolt D.

The lever L extends forwardly beyond the notch L3 and is bent upwardly to form a nose L4 so that normally the end thereof lies in the path ofthe lug D11 on the blot, the end being rounded so that it does not act as a catch to prevent reciprocating movement of the bolt. The lug D11 does, however, when it engages the nose L4, cause downward movement thereof, that is, rotation of the lever L in a counter-clockwise direction about its pivot J2, the downward movement being sufficient to free the step K6 from the notch L3. The sear thus returns to its operative position automatically and even though the trigger may still be depressed, engages the lug D11 as the bolt is moved forwardly by the return spring D1 after the recoil following firing. As thus far described the trigger mechanism is set for single shot firing of the gun.

The arm K4 of the searcarries near its end a. horizontal pivot pin for the bell crank lever, K2, which may comprise va stiff spring steel wire coiled to form the lever pivot bearing, with one arm K'I bent to engage the under' surface of the lever L whilst the other arm K8 is bent to form an attachment hook for the forward end of the `tension spring L2. This spring thus serves three purposes, namely asa return spring for both Athe trigger J and the sear K and also as a return spring for the actuating lever L since, due to the upward pressure exerted on the underside of the lever by the arm K", the upper surface is maintained in contact with the step K6 on the sear -and the lever is moved upwardly following depressionthereof by the lug D11.

In order that the lever L may also act as a selecting member for automatic andsingle shot 1 firing, the lug D11 is, as shown most clearly in Figures 2 and 3, unsymmetrically arranged so that by transverse movement of the forward end of the actuating lever, the nose L4 can be brought `into a position in which it is not engaged by the the bolt is free to move backwards and forwards as long as the trigger J is held depressed, and the' gun fires automatically.

Selecting movement of the lever L is effected by a transverse pin L1 (Figure 2) which is supported by the walls H2 and H3, so that it can slide longitudinally between two limiting positions respectively determined by a collar L5 formed on the pin and by a vsplit ring L6 in an annular groove, the collar and the 'ring being on opposite sides of the wall H2. The pin L1 has an annular groove L" .Which constitutes a guide channel for the lever L so that longitudinal movement of the pin causes transverse movement of the lever between two positions in which the nose L1 is respectively in the path and out of the path of the lug D11. The pin is held in each `of its two positions by ballcatches 4L8 arranged so that the balls engage the edges of the side wall H3.

Itis to be understood that the specific constructions described above are by way of vexample only and that the form of the individual components may be varied as necessary within the scope of the invention as dened in the appended claims.

We claim as our invention:

1. In an automatic firearm having a bolt which reciprocates automatically on firing, a trigger mechanism comprising a trigger, a piv'- oted sear having one arm for holding the bolt in the cocked position and a projection on the other arm, an actuating lever, a notch in said lever arranged to engage said projection, said lever being pivoted at its rear end on the trigger so that operation of the trigger causes said lever to move forwardly to rotate the Sear through the medium of said projection and notch and release the bolt, a bell-crank lever mounted on said other arm of the sear, one arm of the bell crank lever being arranged to engage said actuating lever, a spring connected between the other arm of the bell-crank lever and the trigger so 40 that the first-mentioned arm of the bell-crank lever exerts pressure on said actuating lever to force said notch into contact with said projectrigger mechanism comprising a casing, a trig-y ger, a pivoted sear having one arm for holding the bolt in the cocked position and a projection onthe other arm, an actuating lever, a notch in said lever arranged to engage said projection,

Asaid lever being pivoted at its rear end on the trigger so that operation of the trigger causes said lever to move forwardly to rotate the sear through the medium of said projection and notch and release the bolt, an upturned forward end on said lever, a bell-crank lever mounted on j said other arm of the sear, one arm of the bell crank lever being arranged to engage said actuating lever, a spring connected between the other arm of the bell-crank lever and the trigger vso that the rst-mentioned arm of the bell-crank lever exerts upward pressure on said actuating lever to force said notch into engagement with said projection, a lug on the bolt, and a transverse selector pin slidably mounted in said casing and engaging said actuating lever, which pin can be moved to shift said actuating lever transversely into a position in which said upturned forward end is struck by said lug to disengage said notch and projection against the action of the bell-crank lever and thus release the Sear.

REG-INALD VERNON SHEPHERD. HAROLD J OI-DT TURPIN. 

